The present invention relates to a washing/drying process apparatus and a washing/drying method for chemical-solution-washing, rinsing and drying a surface of a substrate such as a semiconductor wafer or a glass substrate for an LCD.
In a process of fabricating a semiconductor device, a washing/drying process apparatus is used in order to remove a contamination such as particles, organic substances or metal ions from the surface of the substrate. An example of the apparatus for washing and drying a semiconductor wafer is a single-wafer-type washing/drying process apparatus for processing wafers one by one within a cup. In the single-wafer-type washing/drying process apparatus, a wafer is rotated, while being held by a spin chuck, and a chemical solution is applied to the surface of the spinning wafer for chemical solution washing. Then, pure water is applied to the washed surface to rinse it. Finally, a dry N.sub.2 gas is applied to dry the wafer surface.
In the conventional apparatus, a chemical solution nozzle, a rinse nozzle and a dry nozzle are provided around the cup. These nozzles are moved between the home position and use position by different drive mechanisms. In this conventional apparatus, a considerable time is needed for switching from the chemical solution nozzle to the rinse nozzle and from the rinse nozzle to the dry gas nozzle. Consequently, so-called a water mark occurs when liquid drops adhering to the surface of the wafer dry naturally. The water mark is a compound of H.sub.2 SiO.sub.3 produced by reaction between oxygen and H2O in the atmosphere and silicon or by precipitation of a very small amount of SiO.sub.2 included in rinse liquid (pure water) on the surface of the silicon wafer. Such a water mark may remain on the wafer surface even after the dry process.
In addition, in the conventional apparatus, when a chemical solution is applied to the rotating wafer, liquid drops separated centrifugally from the wafer adhere to the inner wall of the cup. Repetition of chemical solution wash processes results in adhesion of a great amount of liquid drops on the inner wall of the cup. This may adversely affect the subsequent rinse process. If the chemical solution drops have dried on the inner wall of the cup and their constituent has precipitated, particles of the constituent may occur and contaminate the wafer.
In the conventional apparatus, after the chemical solution wash process, the waste liquid is recovered from the cup and it is reused after regeneration. In the conventional apparatus, a recovery/regeneration apparatus for recovering and regenerating the waste liquid is disposed as a unit separated from the chemical solution wash apparatus and at a separate location. As a result, the conventional apparatus occupies a large area within the clean room. In addition, the length of the waste liquid recovery circuit (recovery piping) and the regenerated chemical solution return circuit (return piping) increases considerably. Thus, such problems will arise as an increase in capacity of a chemical solution supply pump and a variation in temperature of chemical solution.
In the conventional apparatus, in a case where the bottom surface of the wafer is hydrophobic, a process liquid, which has been applied to the bottom surface of the wafer from a bottom-side nozzle, will naturally drop from the bottom surface of the wafer before spreading over the entire bottom surface. In the conventional process apparatus, therefore, the area on the bottom surface of the wafer, which can be effectively washed, is limited.
Furthermore, the bottom surface of the wafer is not uniformly covered with the liquid, and after the process liquid has naturally dropped from the bottom surface of the wafer, the bottom surface of the wafer comes in contact with outside air in the state in which it is wet to some degree. As a result, a great number of gas-liquid interfaces occur on the bottom surface of the wafer and particles will easily occur at the gas-liquid interfaces. Consequently, particles adhere to the bottom surface of the wafer while the wash process is being performed, and the efficiency of the wash process considerably deteriorates.